The role of PHA-4/FoxA transcription factor in establishing the cellular context for in vivo forced transdifferentiation
Transdifferentiation or direct cell reprogramming is the switch from one differentiated cell-type directly into another, which has been effective in producing clinically relevant cell-types by a mis-expression of transcription factors. However, we do not understand how cellular context influences a cell’s susceptibility to be directly reprogrammed. In the nematode Caenorhabditis elegans, ectopic expression of an intestine-specific GATA transcription factor, end-3, results in the pharyngeal and uterine cells transdifferentiating into intestinal cells. PHA--4/FoxA is a transcription factor that is expressed exclusively in the intestine, pharynx, and uterus. We hypothesize that PHA--4 may have a role in establishing the cellular context that results in transdifferentiation into intestine. We are testing this hypothesis by determining the reprogramming susceptibility of the pharynx and uterus after knocking down PHA--4 using feeding RNA interference. We will induce GATA factor expression via a heat--shocking inducible promoter in PHA--4 depleted larvae and determine if pharyngeal or uterine cells maintain expression of elt-2::GFP, a transgenic reporter that is normally expressed exclusively in the intestine. Our findings showed that there was an increase in the expression of elt-2::GFP within the pharynx and uterus, which indicates that PHA--4 may not have a role in establishing the cellular context that results in transdifferentiation but may instead have the opposite effect of maintaining cellular identity to prevent transdifferentiation. Our next step is to see why there was an increase rather than a decrease in elt-2:GFP expression in pharyngeal and uterine cells. Since there is a conserved role of FoxA and GATA transcription factors in the development of the digestive tract from worms to humans, our future work may help direct methods for interconverting digestive tract models to create clinically pertinent cells.